How can I join a String array with a separator in Java?

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If you’re working on a project that already uses Apache Commons Lang, there’s no reason to reinvent the wheel. Just use StringUtils.join():

import org.apache.commons.lang3.StringUtils;

String[] words = {"a", "b", "c"};
String result = StringUtils.join(words, ",");
System.out.println(result); // Output: a,b,c

This is great because StringUtils.join() works seamlessly with different types of collections and handles null values gracefully. If your project already has Commons Lang, this is an easy win.